This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art.
In recent years, there have been significant concerns about greenhouse gas (“GHG”) emissions and their effect on climate. GHGs, especially carbon dioxide, but also methane and nitrous oxide, trap heat in the atmosphere and thus contribute to climate change. One of the largest sources of GHG emissions is the production and use of fossil fuels for transportation, heating and electricity generation.
Significant efforts have been devoted to reducing the GHG emissions that are associated with production and use of transportation fuels. Renewable fuels, for example, are being used to displace fossil fuels in the transportation sector. Cellulosic biomass has garnered particular attention in this regard due to its abundance and the versatility of the various constituents found therein, particularly cellulose and other carbohydrates. Despite promise and intense interest, the development and implementation of bio-based fuel technology has been slow. Existing technologies have heretofore produced fuels having a low energy density (e.g., bioethanol) and/or that are not fully compatible with existing engine designs and transportation infrastructure (e.g., methanol, biodiesel, Fischer-Tropsch diesel, hydrogen, and methane). Moreover, conventional bio-based processes have typically produced intermediates in dilute aqueous solutions (>50% water by weight) that are difficult to further process. Energy- and cost-efficient processes for processing cellulosic biomass into fuel blends having similar compositions to fossil fuels would be highly desirable to address the foregoing issues and others.
The United States government, through the Energy Independence and Security Act (“EISA”) of 2007, has promoted the use of renewable fuels with reduced GHG emissions. Some of the purposes of the act are to increase the production of clean renewable fuels, to promote research on and deploy GHG capture and to reduce fossil fuels present in transportation fuels. The act sets out a Renewable Fuels Standard (“RFS”) with increasing annual targets for the renewable content of transportation fuel sold or introduced into commerce in the United States. The RFS mandated volumes are set by four nested fuel category groups, namely renewable biofuel, advanced biofuel, biomass-based diesel, and cellulosic biofuel, which require at least 20%, 50%, 50% and 60% GHG reductions relative to gasoline, respectively. The mandated annual targets of renewable content in transportation fuel under the RFS are implemented using a credit called a Renewable Identification Number, referred to herein as a “RIN,” to track and manage the production, distribution and use of renewable fuels for transportation purposes. RINs can be likened to a currency used by obligated parties to certify compliance with mandated renewable fuel volumes. The EPA is responsible for overseeing and enforcing blending mandates and developing regulations for the generation, trading and retirement of RINs.
In addition to EISA, numerous jurisdictions, such as the state of California, the province of British Columbia, Canada and the European Union, have set annual targets for reduction in average life cycle GHG emissions of transportation fuel. Such an approach is often referred to as a Low Carbon Fuel Standard (“LCFS”), where credits may be generated for the use of fuels that have lower life cycle GHG emissions than a specific baseline fuel. Such fuels are often referred to as having a lower “carbon intensity” or “CI”.
Accordingly, the efficient conversion of cellulosic biomass into fuel blends and other materials that meet certain government environmental regulations is a complex problem that presents immense engineering challenges. The present disclosure addresses these challenges and provides related advantages as well.